Material turns 'schizophrenic' on way to superconductivity

(Phys.org) —Rice University physicists on the hunt for the origins of high-temperature superconductivity have published new findings this week about a material that becomes "schizophrenic"—simultaneously exhibiting the characteristics of both a metallic conductor and an insulator.

In a theoretical analysis this week in Physical Review Letters (PRL), Rice physicists Qimiao Si and Rong Yu offer an explanation for a strange series of observations described earlier this year by researchers at the Stanford Linear Accelerator Center in Menlo Park, Calif. In those experiments, physicists used X-rays to probe the behavior of electrons in superconducting materials made of potassium, iron and selenium. The material becomes superconducting at extremely cold temperatures, and the experiments revealed that at a slightly higher temperature, the material exhibited a "schizophrenic" electronic state in which some electrons in the iron atoms became frozen in place while electrons in neighboring orbitals continued to move.

"We have proposed a uniﬁed phase diagram for the alkaline iron selenides in which this schizophrenic phase connects between the lower-temperature, superconducting phase at one extreme and a higher-temperature insulating phase at the other," said Si, Rice's Harry C. and Olga K. Wiess Professor of Physics and Astronomy.

Flowing electrons power all the world's energy grids, and a significant amount of power in those grids is lost to electrical resistance—a kind of electronic friction that occurs when electrons move through metallic wires. Superconducting materials, which were discovered more than a century ago, conduct electricity without any loss of power, but they only operate at extremely cold temperatures. Since the 1980s, scientists have discovered a number of new materials that become superconducting at temperatures that, while still cold, are above or close to the temperature of liquid nitrogen—an important threshold for engineering applications. The hope is that these "high-temperature" superconductors may one day be used to revolutionize power transmission and other technologies, but physicists have yet to develop a clear-cut understanding of how high-temperature superconductors work.

In classical superconductors, frictionless conduction is achieved when electrons pair up in a way that allows them to flow effortlessly, without the bumping and jostling that normally leads to electrical resistance. Electron pairing is uncommon because the rules of quantum mechanics typically make electrons loners. Under normal circumstances, electrons repel one another, and the mechanism that causes them to pair up in classical superconductors doesn't account for their behavior in high-temperature superconductors.

Iron-based high-temperature superconductors were discovered in 2008. Si and collaborators, including UCLA physicist Elihu Abrahams, were among the first to propose a way in which superconductivity might arise in the iron-based materials due to a phenomenon known as "correlated electron" behavior. In correlated-electron systems, the behavior of electrons in a material can only be understood by viewing the electrons as a collective system rather than many individual objects.

Si and Yu's new paper focuses on experiments with an alkaline iron selenide, one family of materials that is included in the larger class of iron-based superconductors. Prior experiments had found that alkaline iron selenides exhibited odd electronic behaviors at temperatures above the critical temperature in which they transition to the superconducting state.

In the PRL paper, Si and Yu describe a new electronic state, or phase, marked by electronic traffic congestion. They show that electrons in different quantum states, or orbitals, react differently to the bad traffic situation. In particular, the new phase is marked by electrons in selected orbitals becoming locked in a place—a phenomenon known as a Mott insulating state.

"In a theoretical model containing several orbitals, we identified an 'orbital-selective Mott phase,'" said Yu, a postdoctoral research associate at Rice. "In this phase, electrons in some orbitals behave like an insulator, while those in the other orbitals act as a metal."

Si and Yu said they saw the first hints of the new phase in a 2011 model they designed to study a different family of iron-based superconductors. In that model, the orbital-selective Mott phase ultimately proved to be unstable, so they were somewhat surprised when the phase appeared and proved stable in the model for the alkaline iron selenides.

"This is the first time anybody has identified an orbital-selective Mott phase in any model for the iron-based superconductors," Yu said.

Si said characterizing the schizophrenic phase in the alkaline iron selenides provides more clues about the fundamental origins of superconductivity.

"Ultimately, our goal is to understand superconductivity and the conditions to optimize superconductivity," Si said.

The premise is that this kind of bad traffic situation—the schizophrenic phase where electrons are in conflict as to whether they should freeze or move—is good for superconductivity.

"Our results provide evidence that electron correlations play a vital role in the superconductivity of the iron-based superconductors," he said.

The debate over the mechanism that causes superconductivity in a class of materials called the pnictides has been settled by a research team from Japan and China. Superconductivity was discovered in the pnictides only recently, ...

An international team of physicists from the United States and China this week offered a new theory to both explain and predict the complex quantum behavior of a new class of high-temperature superconductors.

(PhysOrg.com) -- New experiments on a recently discovered class of iron-based superconductors suggest that the ability of their electrons to conduct electricity without resistance is directly connected with the magnetic properties ...

Japanese and U.S. physicists are offering new details this week in the journal Nature regarding intriguing similarities between the quirky electronic properties of a new iron-based high-temperature superconductor (HTS) and ...

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22 comments

They should say it has a multiple-personality disorder. Schizophrenia has more to do with not being able to tell the difference between reality and fantasy, nothing to do with having a split personality.

In this phase, electrons in some orbitals behave like an insulator, while those in the other orbitals act as a metal

It is clear enough from the Modified Band Theory of Minich. Some "orbitals" differs in wave vector and so belong to insulating wave vectors, or superconducting wave vectors, or to normal metal wave vectors.http://physicsfor...sy.htm#5

This is an apparent nonsense, as the electrons are always repulsive (not surprisingly it was upvoted at PO..;-)). But the binding electrons do mediate the attractive forces between electrons and protons inside of atom nuclei, so such an electrons can be considered as the second type here.

"This is the first time anybody has identified an orbital-selective Mott phase in any model for the iron-based superconductors,"

It is not just valid for the iron-based superconductors. All superconductors are Mott-phases. The charge-carriers are NOT paired electrons but STATIONARY orbitals at localized positions: Superconduction occurs when the distances between the Mott-orbitals become less than a critical distance. If at a higher temperature the distances are larger, and no thermal hopping is present, the material will be an insulator: Just as is found in this case.

The model that fully explains all superconductors with a single Mott-tunneling mechanism is already 8 years old; but is censored from being published since it is not based on fictitious pair formation: We could already have had a thriving industry based on room temperature superconductors if the mainstream idiots would just let go of "pair-formatation"See:http://www.cathod...nism.pdf

the charge-carriers are NOT paired electrons but STATIONARY orbitals at localized positions

It can be both because of intrinsic spin of electrons. In Colin Humprey's theory based on magnetic pairing superconductor consists of square "nanodomains", separated by channels that are one unit-cell wide - rather like a grid of streets surrounding blocks of houses. Holes at the edges of adjacent blocks are magnetically paired, and superconductivity occurs because these hole-pairs march collectively along the channels, like trams on pairs of tramlines running between the blocks of houses. There is one hole on each tramline, according to the model, and the pairs of holes move down the channels, hopping from block to block. Another results consistent with magnetic pairing.

First it is ducks paddling in the aether, and now it is trams running along streets surrounding blocks and houses! Please try and escape from Voodooland!

Try and do some mathematics and to fit your ideas to actual data; as I have done and am still doing with my model in order to prove that it explains all known data on all known superconductors quantitatively.

Wrong! Well renowned physicist with a successful career and citation index advises a deranged crackpot youngster who obviously has no scientific insight that he is not contributing anything fundamental or quantitative by what he is posting on this forum.

A successful? The only significant finding of yours is completely ignored by mainstream. From your book it's evident, you're even more upset with mainstream physics, than just me. The people like you are never successful and respected in mainstream science. I can perceive just funny, when the person who hates the mainstream physics so much lays about his "citation index". Nobody takes a shit about it, as you clearly see...;-) After all, what are doing for physics last twenty years? You're only posting to various forums in the same way like me.

The only significant finding of yours is completely ignored by mainstream.

Another lie! Why do you have to blatantly LIE LIE LIE all the time! Do you not have ANY integrity or ANY conscience. Check my CV on my website. http://www.cathod...RVIT.pdf

From your book it's evident, you're even more upset with mainstream physics, than just me.

YOU have NEVER read my book to make this judgement! Further proof of your dishonesty!

The difference between YOU and me is that I have valid reasons to be upset, while YOU do not; since YOU are a REAL crackpot who gives NO quantitative arguments to support your hallucinations of ducks and tramlines!

After all, what are doing for physics last twenty years? You're only posting to various forums in the same way like me.

Another LIE!! PLEASE go and see a psychiatrist: YOU are VERY VERY ILL!!

I have already posted before (if you will just open your eyes) that the experiment has been independently replicated at the request of our Electricity Utility Company; and exactly the same results were found. In fact they also have photographs of the phase between the diamond's surface and of magnetic dust floating around it.

http://www.ncbi.nlm.nih.gov/pubmed/10927254 has such quantitative arguments - it's his theory, not mine.

And you are incapable of judging any of his wrong arguments!

Note that he essentially predicted the finding announced in the above article.

No he DID NOT: Only a demented mind will come to the latter conclusion.

I'd say, it's rather you who is mentally unstable here - you've been reported, as I promised.

For posting the truth in an effort to help you! Your crackpottery is the reason why the mainstream scientists suspect that any new ideas are crackpot!

the experiment has been independently replicated at the request of our Electricity Utility Company; and exactly the same results were found. In fact they also have photographs of the phase between the diamond's surface and of magnetic dust floating around it

This is great, but I'm missing a link to these results and photos. Did they try the nonmagnetic dust too? It could be charge effect of holes implanted bellow surface of diamond. This is an example of particles levitating above electrode and absolutely no superconductivity is present there.

The data was paid for by ESKOM and belong to them. If ESKOM does not want to publish it for some commercial reason, I cannot force them to do so. I have asked them for the photographs: Maybe they will relent in future!

Did they try the nonmagnetic dust too?

The floating powder only formed when the anode was a magnetic metal. The SC phase then formed a small gap with the anode across which electrons jumped to sputter-form the magnetic powder. When using a non-magnetic anode this does not occur.

It could be charge effect of holes implanted bellow surface of diamond.

No it is not the case since the phase must first form as a black rod connecting the diamond and the anode before the magnetic powder accumulates around the black rod.

The impeccable physics of dipole interfaces proves that the black rod can only form from electrons supplied by a depletion-layer below the diamond's surface; and can only exist when the dipole cancels an applied electric-field within it totally by means of its own polarization field. Thus it is physically impossible that there can be an electric-field within such a dipole (i.e. no voltage across the dipole). And yet a current is flowing through the dipole. It is the best proof EVER that superconduction is occurring! It has NEVER been proved for any other superconductor that the voltage across two contacts MUST be zero.

It is so simple I should have predicted the result without even doing the experiment: May I refer you yet again to:

This "electronic traffic congestion" report is consistent with the theory that I have advanced many times on PhysOrg. My theory is that high temp superconductivity arises when electrons self-organize according to Art Winfree's "law of coupled oscillators," which he articulated circa 1967.

Winfree's law explains how any system of limit cycle oscillators will tend to self-organize, and do so in certain precise patterns. The simplest such pattern is 0 and 180 degrees: precisely synchronous and antisynchronous; others are available also.

"Odd electronic behaviors at temps above the critical temp in which they transition to the superconducting state." That is the "schizophrenic," insulator or metal, "orbital selective Mott phase." "The bad traffic situation is..."good for superconductivity." Yes, it is--because below the critical temp Winfree's law creates a "correlated electron system," behaving as a system rather than individual objects." Non-linear self-organization: Macksb-Winfree.

when electrons self-organize according to Art Winfree's "law of coupled oscillators,"

So why/when the electrons self-organize? Why they self-organize in niobium, not in sodium, for example? And what we can deduce from it? Your model is string theory-like model. It explains nothing testable, it predicts nothing testable.

The full article is available on Arxiv. Google Lu Si Orbital-selective Mott Phase

In any system of correlated limit-cycle oscillators (e.g., electrons) the organization will follow Winfree's law. Every time...no exceptions. I first proposed a correlated electron explanation for superconductivity, based on Winfree's law, many years ago. The specific observations made in the above article do not necessarily prove my proposition, but they come darn close. The only way to get from a world of traffic collisions to a world in which there are no collisions of any kind is via Winfree's law of coupled oscillators.

Steve Strogatz and Ian Stewart wrote a Scientific American article about Winfree in December 1993. A copy is available online at a math.oregonstate.edu site. Winfree developed the idea mathematically and applied it exclusively to biology. He was an early bio-mathematician. But math is math, and math goes best with physics.

In any system of correlated limit-cycle oscillators (e.g., electrons) the organization will follow Winfree's law

But we already know for many years, that the (motion of) electrons remain correlated inside of superconductors - their charge is transfered in waves, i.e. like bosons, because they're forming boson condensate there. It's not an explanation, it's a description of superconductivity state. You should be able to predict, when such organization will occur with using of easily accessible/measurable material parameters, or such a model will not be falsifiable, not to say about its practical usefulness.

math is math, and math goes best with physics

Unfalsifiable math without testable predictions is just a philosophy or dice throwing. The physics is experimental science - not a void numerology (despite many modern physicists pretend the opposite). The derivation of equations is very safe job, until you're not confronted with experiments.

Thanks for the challenges Valeria. I will answer them one by one. "Unfalsifiable math"? No. The math was developed by Art Winfree, a MacArthur prize winner. Strogatz, Mirollo and Kuramoto, among others, have all validated, extended and applied that math, successfully. "Without testable predictions"? No. I have advanced this same theory, which makes predictions, fifty or more times on PhysOrg, and on other occasions in other physics blogs. All easy to find.

"Until you're confronted with experiments"? No. The experiments are all consistent with the theory and its predictions. Again, this is all public. See my 50 or more posts on PhysOrg, at least 35 of which state my theory and show why it is consistent with particular PhysOrg articles--all of which describe results that the physicists claim (not always correctly) to be unexpected.

We agree on one point--my theory is "string-theory like." String theory concerns vibrating (oscillating) strings. That's a big plus, not a minus.

Here's another example--one which arose after my two comments above: "Molecular Rings Mystery Solved After 20 Years," PhysOrg April 16. Read the article and see my comment about how Art Winfree's 1967 law of coupled oscillators predicted the mystery and its solution.

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